Reference Literature 1 (Japanese Unexamined Patent Application Publication No. 2008-78887) discloses a system for sharing input/out devices as well as for sharing information processing apparatuses using the PCI Express (Peripheral Component Interconnect Express) standard. The system is configured by connecting a bridge disposed on the processor side with a bridge disposed on the input/out device (hereinafter denoted as I/O (Input/Output) device) side via Ethernet®. In this system, an input/output request which is issued by the processor toward the I/O device is encapsulated into an Ethernet frame by the bridge disposed on the processor side and then sent to the bridge disposed on the I/O device side.
The left-hand area (to the left of the arrow) of FIG. 11 represents a system configuration based on the technique disclosed in Reference Literature 1. The system is configured by connecting the bridge connected on the server side (ExpEther® Server card; hereinafter abbreviated as EESV) with the bridge connected on the I/O device side (ExpEther I/O card; hereinafter abbreviated as EEIO) via a layer 2 switch (L2 switch).
The system allows for grouping of a central processing unit (CPU) and I/O devices. For example, assuming that EESV 0, EEIO 0, EEIO 2, and EEIO 3 belong to Group 0 while EESV 1 and EEIO 1 belong to Group 1, the system can group CPUs and I/O devices, each of which is connected to its bridge, into Group 0 and Group 1.
That is, CPU 0 and I/O Devices 0, 2, and 3 belong to Group 0 while CPU 1 and I/O Device 1 belong to Group 1, which is equivalent to the representation on the right-hand area (to the right of the arrow) of FIG. 11 illustrating separate configurations by group. Thus, systems based on the ExpEther technology allow for flexible configurations.
The system shown in FIG. 11 determines a group for each EEIO. A user directly connects I/O devices individually with each EEIO so that grouping can be performed for each I/O device. Such configuration requires the user to add an EEIO for every additional I/O device, resulting in higher cost.
On the other hand, FIG. 12 shows that a user can connect a large number of I/O devices under one EEIO by connecting a PCI Express switch (hereinafter denoted as PCIe switch) to the EEIO. That is to say, the user can add I/O devices at low cost. In this case, however, the system cannot perform grouping for each I/O device.
In other words, the system employing the technique disclosed in Reference Literature 1 cannot achieve low-cost addition of I/O devices while maintaining the flexibility of system configurations.
In addition, Reference Literature 2 (Japanese Unexamined Patent Application Publication No. 2012-146088) discloses a communication control system which allows for synchronization adjustment for every combination of devices. The communication control system is configured by connecting the bridge disposed on the processor side with the bridge disposed on the I/O device side via a network.
Reference Literature 3 (Japanese Unexamined Patent Application Publication No. 2010-282387) discloses a computer system which eliminates a single point of failure in a management virtual switch in a multi-root PCI switch.